1. Field of the Invention
The present invention relates to a portable communication apparatus and a microphone device for the apparatus. In the portable communication apparatus and the microphone device for the apparatus according to the invention, an openable/closable member which incorporates a microphone is attached in an openable and closable manner to the main unit of the portable apparatus so that, in both the cases where the openable/closable member is opened, and where the member is closed, a speech quality of a very high S/N ratio can be obtained at a substantially same degree.
2. Description of the Prior Art
Japanese Patent Application Laying-Open No. 11-32107 (first prior art example) discloses a portable communication apparatus. In the disclosed portable communication apparatus, a microphone is incorporated into a flip which is screwed in an openable and closable manner to the main unit of the apparatus, and a sound-pick up hole for enabling the microphone to pick up a sound is opened in each of inner and outer flips of the flip, so that, when the flip is closed, the microphone can pick up a sound through the sound-pick up hole of the outer flip, and, when the flip is opened, the microphone can pick up a sound through the sound-pick up hole of the inner flip. In the publication, a cordless telephone and a portable telephone are indicated as the portable communication apparatus, and it is described that the portions where the sound-pick up holes of the outer and inner flips are opened are located in places which are close to the free end which is remote from the center position of the opening and closing movements of the flip.
Japanese Patent Application Laying-Open No. 11-308314 (second prior art example) discloses a telephone apparatus. In the telephone apparatus, a close-talking microphone (close-talking electret condenser microphone) having sound holes which are respectively in sides sandwiching a diaphragm is placed inside a movable member which is openably and closably attached to the main unit, and the sound holes are located in places which are close to the free end of the movable member. In the telephone apparatus, when the movable member is closed, one of the sound holes is closed and the other sound hole remains opened, so that the close-talking microphone functions as an omnidirectional microphone, and, when the movable member is opened, both the sound holes remain opened, so that the proximity effect is produced for a sound source close to one of the sound holes, to improve the speech quality.
Japanese Patent Application Laying-Open No. 11-177664 (third prior art example) discloses a microphone device for a portable telephone. According to the publication, an ominidirectional microphone is incorporated in a flip which covers the front face of a portable telephone in a manner similar to a folding type one, and sound holes are formed respectively in the front and back faces of a center portion in the longitudinal direction of the flip. In the microphone device for a portable telephone, both a sound wave which passes through the sound hole of the front face of the flip, and that which passes through the sound hole of the back face of the flip reach the front face of the ominidirectional microphone.
However, the first to third prior art examples have the following problems.
In the portable communication apparatus of the first prior art example, both the sound-pick up holes which are respectively formed in the outer and inner flips constituting the flip are positioned in places which are close to the free end of the flip. In the case where the sound-pick up holes are configured so that, when the flip is opened, the sound-pick up hole of the inner flip is positioned in the vicinity of the mouth, for example, the sound-pick up hole of the outer flip is remote from the mouth when the flip is closed. Therefore, the difference between the sound pressure applied to the microphone in the case where the flip is opened, and that in the case where the flip is closed becomes large, thereby causing a problem in that the speech qualities in the cases are remarkably different from each other. In the case where a close-talking microphone is used as the microphone incorporated in the flip as shown in the second prior art example, when the flip is closed, therefore, the mouth (sound source) is positioned in a place which is remote from the diaphragm of the close-talking microphone, and hence it seems that the sensitivity of the close-talking microphone is not enhanced and the speech quality is remarkably lowered.
The telephone apparatus of the second prior art example is configured so that, only when the movable member is opened, the close-talking microphone exerts the proximity effect, and, when the movable member is closed, the close-talking microphone functions as an ominidirectional microphone. Although a close-talking microphone is employed, when the movable member is closed, therefore, it is impossible to exert the effect of improving the speech quality by the proximity effect of the close-talking microphone. In the second prior art example, even if a configuration is assumed in which the proximity effect of the close-talking microphone can be exerted in both the cases where the movable member is opened, and where the member is closed, the proximity effect of the close-talking microphone cannot be expected in the case where the apparatus is configured so that, when the movable member is opened, the mouth is positioned in the vicinity of the sound hole and the close-talking microphone can exert the proximity effect. This is because of the following reason. When the movable member is closed, the mouth is remote from the sound holes because both the sound holes of the inner and outer sides in the close-talking microphone are positioned in the vicinity of the free end of the movable member.
In the microphone device for a portable telephone of the third prior art example, since the sound holes are formed respectively in the front and back faces of a center portion in the longitudinal direction of the flip, the positional relationship between the mouth and the corresponding sound hole when the flip is closed is identical with that when the flip is opened. However, the route along which a sound wave reaches the diaphragm of the microphone incorporated in the flip when the flip is opened is different from that when the flip is closed. When the flip is closed, particularly, a sound wave which passes through the sound hole of the back face of the flip reaches the front face of the microphone with going around the periphery of the case of the microphone. Therefore, it seems that, when the flip is closed, the speech quality is lowered.